Abstract: The beach-bar sand depositional assemblage was identified from Badaowan formation in Sishilicheng slope belt of Yanqi basin.These sand bodies were coexisted with effective source rocks and had characteristics of good reservoir properties and good source-reservoir-caprock assemblage,which was good for lithologic reservoir accumulation.Little affected by late tectonic movement and destruction,the conservation conditions in the late stage were good.The comprehensive exploration of the beach-bar sand bodies was expected to open a new exploration area in Yanqi basin.The research results indicated in addition to adequate sediment provenance,the good hydrodynamic conditions and the suitable paleogeomorphic environment,the development of the beach-bar sand bodies in study area was also closely related to the development of the slope break belt and the forced regression.